|Collins, F William|
Submitted to: Nutrition and Cancer
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2010
Publication Date: 11/6/2010
Publication URL: http://naldc.nal.usda.gov/catalog/48388
Citation: Guo, W., Nie, L., Wu, D., Wise, M.L., Collins, F., Meydani, S., Meydani, M. 2010. Avenanthramides inhibit proliferation of human colon cancer cell lines in vitro. Nutrition and Cancer. 62(8):1007-1016. Interpretive Summary: High intake of whole grain food is associated with reduced risk of colon cancer, but the kind of nutrient components in the food that gives the health benefits needs to be clarified. We found that compounds from oats, called avenanthramides (Avns), suppressed activity of a protein in macrophages called COX enzyme. Macrophages are immune cells that destroy harmful microorganisms in the body. It is believed that the COX enzyme participates in the development of cancer in digestive tract. We tested three forms of Avns, and found that all three forms of Avns significantly inhibited four kinds of human colon cancer cell growth. Avns did no harm to normal cells in the digestive tract. We know that the high fiber content of oats contributes to health benefits, but our discovery also suggests that the consumption of oats and oat bran may reduce the risk of colon cancer through suppression of cancer cell growth in the colon. Our findings also provide a basis for developing medicines from natural sources that prevent and treat for colon cancer.
Technical Abstract: High intake of whole grain food is associated with reduced risk of colon cancer, but the mechanism underlying this protection has yet to be elucidated. Chronic inflammation and associated cyclooxygenase-2 (COX-2) expression in the colon epithelium are causally related to epithelial carcinogenesis, proliferation, and tumor growth. We examined the effect of avenanthramides (Avns), unique polyphenols from oats with anti-inflammatory properties, on COX-2 expression in macrophages, colon cancer cell lines, and on proliferation of human colon cancer cell lines. We found that Avns enriched extract of oats (AvExO) had no effect on COX-2 expression, but inhibited the COX enzyme activity and prostaglandin E2 (PGE2) production in LPS-stimulated mouse peritoneal macrophages. Avns (AvExO, Avn-C, and the methylated form of Avn-C (CH3-Avn-C)) significantly inhibited cell proliferation of both COX-2-positive HT29, Caco-2, and LS174T, and COX-2-negative HCT116 human colon cancer cell lines, with CH3-Avn-C being the most potent. However, Avns had no effect on COX-2 expression and PGE2 production in Caco-2 and HT29 colon cancer cells. These results indicate that the inhibitory effect of Avns on colon cancer cell proliferation may be independent of COX-2 expression and PGE2 production. Thus, Avns might reduce colon cancer risk through inhibition of macrophage PGE2 production and non-COX-related antiproliferative effects in colon cancer cells. Interestingly, Avns had no effect on cell viability and proliferation of confluence-induced differentiated Caco-2 cells, which display the characteristics of normal colonic epithelial cells. Our results suggest that the consumption of oats and oat bran may reduce the risk of colon cancer not only through high fiber content but also through Avns, which attenuates proliferation of colonic cancer cells.